Preparation method of palladium ion imprinted resin and method for recovering palladium in silver electrolyte by using the same

Abstract

This invention belongs to the field of non-ferrous metal smelting, specifically relating to a method for preparing palladium ion-imprinted resin and a method for recovering palladium from silver electrolyte using it. Utilizing the specific recognition ability of the palladium ion-imprinted resin, it selectively adsorbs only palladium ions, while impurity ions such as silver and copper are almost not adsorbed, significantly reducing silver loss. A thiourea-hydrochloric acid mixture is used as the eluent, offering high elution efficiency and recyclability. This method avoids the oxidation of palladium ions at the anode, while simultaneously increasing the palladium concentration, laying the foundation for subsequent chemical purification. Nitrogen protection further reduces palladium oxidation loss. A stepwise process of ammonia complexation-hydrochloric acid acidification-hydrazine hydrate reduction is employed to achieve deep purification of palladium, yielding high-purity palladium powder. This invention involves no toxic reagents throughout the process, meeting green production requirements. It enables precise separation and high-purity recovery of palladium while ensuring efficient retention of silver resources, balancing process safety and industrial feasibility.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting, specifically relating to a method for preparing palladium ion imprinted resin and a method for recovering palladium from silver electrolyte using the resin. Background Technology

[0002] In silver electrolytic refining, palladium from the anode dissolves into the electrolyte along with the silver. This accumulation of palladium not only reduces the purity of the electrolytic silver product but also wastes this precious metal. Existing palladium recovery methods have several shortcomings: solvent extraction easily traps silver ions, leading to high silver loss rates, and the extractant introduces volatile pollutants; chemical precipitation methods have poor selectivity, resulting in high impurity content in the precipitate and cumbersome subsequent purification steps; displacement methods introduce new metallic impurities, affecting the quality of the palladium product. Furthermore, some processes use toxic reagents such as cyanide, posing significant safety and environmental risks.

[0003] Chinese invention patent application entitled "A Method for Separating Palladium from Silver Electrolyte" (publication number CN102329959A) discloses a method for separating palladium from silver electrolyte using modified polyacrylonitrile resin. In this method, polyacrylonitrile resin is modified with hydrochloric acid hydroxylamine solution to obtain a novel chelating resin—a methylamine oxime polyacrylonitrile resin. The methylamine oxime polyacrylonitrile resin is used to adsorb the silver electrolyte that has been preliminarily purified to remove heavy metal impurities, thereby loading palladium in the solution onto the resin. Then, an acidic thiourea solution is used for a first desorption to obtain a palladium-containing desorbent, and a high-concentration hydrochloric acid solution is used for a second desorption to obtain a silver-containing desorbent. After the two desorptions, the resin is regenerated with hydrochloric acid hydroxylamine solution and then returned to the resin to adsorb the palladium-containing silver electrolyte. Although this scheme achieves the separation of silver and palladium, on the one hand, the silver electrolyte needs to be deimpurified before resin adsorption; on the other hand, the modified resin used not only adsorbs palladium, but also has an adsorption effect on silver and copper in the silver electrolyte. After eluting palladium ions, silver ions and copper ions need to be eluted separately, which is cumbersome and costly.

[0004] Therefore, developing a palladium recovery process that is highly selective, has low silver loss, and is environmentally friendly is of great significance for improving the quality and efficiency of the silver electrolytic refining industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a palladium ion imprinting resin with a high selective recognition ability for palladium ions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing palladium ion imprinted resin, comprising the following steps:

[0007] A) Preparation of the prepolymerization system: Add 2-4 mmol / L of dimethylglyoxime to a palladium ion standard solution with a concentration of 0.5-1.0 mmol / L, and stir for 30-40 min; then add 10-15 mmol / L of ethylene glycol dimethacrylate and 0.05-0.1 mmol / L of 2,2-azobisisobutyronitrile, and continue stirring for 15-20 min to obtain the prepolymerization system mixture;

[0008] B) Precipitation polymerization reaction: After purging the prepolymer system mixture with nitrogen to remove oxygen for 20-30 minutes, the temperature is raised to 60-65℃ and polymerized at a constant temperature for 6-8 hours under nitrogen protection.

[0009] C) Template ion elution: After the polymerization reaction is completed, filter, wash the precipitate with ethanol, soak in a 5-8% thiourea-hydrochloric acid mixture for 8-10 hours, filter, wash the precipitate with deionized water until the pH of the filtrate is neutral, and obtain the eluted polymer.

[0010] D) Drying and sieving: The eluted polymer is placed in a vacuum drying oven at 60-70℃ and dried for 12-16 hours. After drying, it is sieved through a standard sieve to collect particles with a diameter of 0.3-0.8 mm, which are palladium ion imprinted resins.

[0011] The preparation method is simple, and the prepared palladium ion imprinted resin has stable physicochemical properties, strong specific recognition ability of palladium ions, and no toxic reagents are involved in the preparation process, which is in line with the concept of green production.

[0012] Specifically, in step (A), the palladium ion standard solution is a palladium ion solution with a concentration of 0.5-1.0 mmol / L, using acetonitrile as the solvent; in step (B), the stirring rate is maintained at 120-150 r / min during the polymerization process; and in step (C), the mixture is stirred once every 1-2 hours during the soaking process.

[0013] The specific adsorption of palladium ion imprinted resin is based on template imprinting and specific recognition mechanisms. During the preparation process, template palladium ions and dimethylglyoxime functional monomers form a stable template-monomer complex through coordination bonds. Subsequently, the complex is fixed in the three-dimensional network structure of polymethyl methacrylate carrier through cross-linking polymerization. When the template ions are eluted, cavities that perfectly match the palladium ions in terms of spatial configuration, size and binding sites are formed inside the resin.

[0014] During the adsorption process in the silver electrolyte, the hole exhibits a high degree of selectivity for palladium ions, allowing only palladium ions to recombine into the hole through coordination. Impurity ions such as silver and copper, due to their mismatched spatial configurations, cannot form stable coordination bonds with the functional monomers and are therefore unable to enter the hole for adsorption. This specific recognition mechanism ensures efficient separation of palladium from impurity ions. Simultaneously, the three-dimensional network structure of the resin support provides stable physical support, guaranteeing mass transfer efficiency during adsorption and laying the foundation for subsequent elution and enrichment steps.

[0015] Another objective of this invention is to provide a method for recovering palladium from silver electrolyte. By utilizing the high selective adsorption of palladium ions by imprinted resin, palladium ions in the silver electrolyte are adsorbed out, thereby achieving efficient separation of silver and palladium. This solves the problems of large silver loss and serious environmental pollution, and achieves accurate separation and high-purity recovery of palladium.

[0016] A method for recovering palladium from a silver electrolyte includes the following steps:

[0017] (1) Pretreatment: After adjusting the pH of the silver electrolyte containing palladium ions to 1-2, sodium bisulfite is added and stirred to dissolve, thus obtaining the pretreated solution;

[0018] (2) Ion imprinted adsorption: The pretreated solution was passed through a palladium ion imprinted resin adsorption column. After adsorption saturation, it was eluted with a 6% thiourea-hydrochloric acid mixture to obtain the eluent.

[0019] (3) Diaphragm electrolytic enrichment: The diaphragm electrolytic cell is divided into a cathode chamber and an anode chamber by a cation exchange membrane. The cathode is a titanium-plated platinum electrode and the anode is a graphite electrode. The eluent is transferred into the anode chamber of the diaphragm electrolytic cell. During the electrolysis process, nitrogen gas is introduced into the cathode chamber. The current density is controlled at 90-110 A / m², the electrolysis temperature is 40-60℃, and the electrolysis is carried out for 2-3 hours. The cathode chamber obtains a palladium-rich solution.

[0020] (4) Chemical purification: Add ammonia to the palladium-rich solution until the pH value is 8-9, stir for 10-40 min, and filter; add hydrochloric acid to the filtrate to acidify until the pH value is 1-2, let stand for 1-2 h to precipitate; wash the precipitate with a mixture of deionized water and anhydrous ethanol, add hydrazine hydrate solution, reduce at 50-80℃ for 20-60 min, filter and dry to obtain palladium powder.

[0021] Specifically, after adjusting the temperature of the silver electrolyte containing palladium ions to 30-40℃, the pH value is adjusted to 1-2 with dilute sulfuric acid; the amount of sodium bisulfite added is 0.01-0.05 g / L.

[0022] In step (2), the chloride ion concentration is controlled at 5-7 g / L during adsorption; preferably 6 g / L, for the following reasons: 1) Palladium ions exist in a stable chloride complex form, which highly matches the recognition holes of the ion-imprinted resin, ensuring high selectivity and high adsorption capacity for palladium; 2) It inhibits the co-adsorption and co-precipitation of impurity ions such as silver and copper, improving the separation efficiency of palladium from impurities; 3) It stabilizes the solution system, reduces the tank pressure, and facilitates subsequent membrane electrolytic purification. The chloride ions mainly come from the chloride ions contained in the silver electrolytic raw solution itself. When the concentration is insufficient, the chloride ion concentration is adjusted by adding hydrochloric acid or sodium chloride.

[0023] The palladium ion-imprinted resin in the adsorption column has a particle size of 0.3-0.8 mm. After the resin adsorption column is saturated, it is eluted with a thiourea-hydrochloric acid mixture with a mass concentration of 6% at a flow rate of 1-2 BV / h.

[0024] In step (3), during the electrolysis process, the nitrogen gas flow rate into the cathode chamber is 0.2-0.4 L / min.

[0025] In step (4), the amount of hydrazine hydrate added is 0.9 times the mass of the precipitate; the volume ratio of water and anhydrous ethanol in the mixture is 1:1.

[0026] The above scheme utilizes the specific recognition capability of palladium ion imprinting resin to selectively adsorb only palladium ions, while impurity ions such as silver and copper are almost not adsorbed, significantly reducing silver loss. A thiourea-hydrochloric acid mixture is used as the eluent, offering high elution efficiency and recyclability. This avoids the oxidation of palladium ions at the anode, while simultaneously increasing the palladium concentration, laying the foundation for subsequent chemical purification. Nitrogen protection further reduces palladium oxidation loss. A stepwise process of ammonia complexation, hydrochloric acid acidification, and hydrazine hydrate reduction is employed to achieve deep purification of palladium, yielding high-purity palladium powder. This invention involves no toxic reagents throughout the process, meeting green production requirements. It enables precise separation and high-purity recovery of palladium while ensuring efficient retention of silver resources, balancing process safety and industrial feasibility. Detailed Implementation

[0027] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0028] Example 1: Preparation of palladium ion imprinted resin

[0029] The palladium ion-imprinted resin used in this invention is prepared by precipitation polymerization using polymethyl methacrylate as a carrier and dimethylglyoxime as a functional monomer. The specific steps are as follows:

[0030] a) Preparation of the prepolymerization system: A 0.5-1.0 mmol / L palladium ion standard solution was added as the template ion to acetonitrile solvent (i.e., a palladium ion-acetonitrile solution with a concentration of 0.5-1.0 mmol / L using acetonitrile as the solvent). Then, dimethylglyoxime functional monomer was added, and the concentration of dimethylglyoxime in the mixed solution after addition was 2-4 mmol / L. The mixture was magnetically stirred at room temperature for 30-40 min to allow the template ion and functional monomer to fully combine and form a complex. Subsequently, 10-15 mmol / L ethylene glycol dimethacrylate crosslinking agent and 0.05-0.1 mmol / L 2,2-azobisisobutyronitrile initiator were added, and stirring was continued for 15-20 min to obtain a homogeneous prepolymerization system.

[0031] b) Precipitation polymerization reaction: Transfer the prepolymerization system to a three-necked flask, purge with nitrogen to remove oxygen for 20-30 min, then heat to 60-65℃ and polymerize at a constant temperature for 6-8 h under nitrogen protection; during the polymerization process, maintain a stirring rate of 120-150 r / min to ensure uniform precipitation of the polymer.

[0032] c) Template ion elution: After the polymerization reaction is completed, the product is filtered and collected, and washed with ethanol 3-4 times to remove unreacted monomers and crosslinking agents; then the product is placed in a thiourea-hydrochloric acid mixture with a thiourea mass concentration of 5-8% and soaked at room temperature for 8-10 hours, stirring once every 2 hours during the soaking period to achieve complete elution of template palladium ions; after elution, the product is washed with deionized water until the pH of the filtrate is neutral.

[0033] d) Drying and sieving: Place the eluted polymer in a vacuum drying oven at 60-70℃ and dry for 12-16 hours. After drying, sieve through a standard sieve and collect particles with a diameter of 0.3-0.8 mm, which are the desired palladium ion imprinted resin.

[0034] Example 2: Recovery of palladium from silver electrolyte

[0035] A method for recovering palladium from silver electrolyte includes the following steps:

[0036] (1) Pretreatment: Take 10L of silver electrolyte with palladium ion concentration of 0.8g / L and silver content of 108g / L, adjust the temperature to 35℃, adjust the pH value to 1.2 with dilute sulfuric acid, add 0.03g / L sodium bisulfite, stir at 180r / min for 12min to obtain pretreated solution;

[0037] (2) Ion imprinted adsorption: The pretreated solution was passed through a palladium ion imprinted resin adsorption column at a flow rate of 3 BV / h. The resin particle size was 0.5 mm. The chloride ion concentration was controlled at 6 g / L during the adsorption process. After the adsorption was saturated, a 6% thiourea-hydrochloric acid mixture was used to elute at a flow rate of 1.5 BV / h, and the eluent was collected.

[0038] (3) Diaphragm electrolytic enrichment: The eluent is transferred to the diaphragm electrolytic cell (the eluent is sent to the anode chamber of the diaphragm electrolytic device, and the cathode chamber is separately added with conductive media such as potassium nitrate, sodium sulfate or dilute nitric acid). The cathode chamber and the anode chamber are separated by a cation exchange membrane. The cathode is a titanium-plated platinum electrode and the anode is a graphite electrode. The current density is controlled at 100A / m², the electrolysis temperature is 50℃, and nitrogen gas is introduced into the cathode chamber (gas flow rate 0.3L / min). Electrolysis is carried out for 2.5h, and a palladium-rich solution with a palladium concentration of 42g / L is obtained in the cathode chamber.

[0039] (4) Chemical purification: Add 1.5 mol / L ammonia to the palladium-rich solution, adjust the pH to 8.2, stir for 25 min, and filter; add 2.5 mol / L hydrochloric acid to the filtrate to acidify to pH 1.2, let stand for 1.5 h to precipitate dichlorodiamminepalladium; wash the precipitate 4 times with a mixture of deionized water and anhydrous ethanol (volume ratio 1:1), then add 12% hydrazine hydrate solution (addition amount is 0.9 times the mass of the precipitate), reduce at 65℃ for 35 min, filter, dry to obtain palladium powder, the purity is detected to be 99.992%, and the palladium recovery rate is 99.6%.

[0040] Example 3: Recovery of palladium from silver electrolyte

[0041] A method for recovering palladium from silver electrolyte includes the following steps:

[0042] (1) Pretreatment: Take 10L of silver electrolyte with palladium ion concentration of 2.5g / L and silver content of 112g / L, adjust the temperature to 38℃, adjust the pH value to 1.4 with dilute sulfuric acid, add 0.04g / L sodium bisulfite, stir at 190r / min for 14min to obtain pretreated solution;

[0043] (2) Ion imprinted adsorption: The pretreated solution was passed through a palladium ion imprinted resin adsorption column at a flow rate of 3.5 BV / h. The resin particle size was 0.6 mm. The chloride ion concentration was controlled at 7 g / L during the adsorption process. After adsorption saturation, 7% thiourea-hydrochloric acid mixture was used for elution at a flow rate of 2 BV / h, and the eluent was collected.

[0044] (3) Diaphragm electrolytic enrichment: The eluent was transferred into a diaphragm electrolytic cell. The cathode was a titanium-plated platinum electrode and the anode was a graphite electrode. The current density was controlled at 110 A / m², the electrolysis temperature was 53 °C, and nitrogen gas was introduced into the cathode chamber (gas flow rate 0.35 L / min). Electrolysis was carried out for 2.8 h to obtain a palladium-rich solution with a palladium concentration of 48 g / L.

[0045] (4) Chemical purification: Add 2 mol / L ammonia to the palladium-rich solution, adjust the pH to 8.4, stir for 28 min, and filter; add 3 mol / L hydrochloric acid to the filtrate to acidify to pH 1.4, let stand for 1.8 h to precipitate dichlorodiamminepalladium; wash the precipitate 5 times with a mixture of deionized water and anhydrous ethanol (volume ratio 1:1), then add 14% hydrazine hydrate solution (addition amount is 1.0 times the mass of the precipitate), reduce at 68℃ for 38 min, filter, dry to obtain palladium powder, the purity is detected to be 99.991%, and the palladium recovery rate is 99.5%.

[0046] Example 4: Recovery of palladium from silver electrolyte

[0047] A method for recovering palladium from silver electrolyte includes the following steps:

[0048] (1) Pretreatment: Take 10L of silver electrolyte with palladium ion concentration of 0.3g / L and silver content of 105g / L, adjust the temperature to 32℃, adjust the pH value to 1.1 with dilute sulfuric acid, add 0.02g / L sodium bisulfite, stir at 160r / min for 11min to obtain pretreated solution;

[0049] (2) Ion imprinted adsorption: The pretreated solution was passed through a palladium ion imprinted resin adsorption column at a flow rate of 2.5 BV / h. The resin particle size was 0.4 mm. The chloride ion concentration was controlled at 5.5 g / L during the adsorption process. After adsorption saturation, a 5.5% thiourea-hydrochloric acid mixture was used to elute at a flow rate of 1.2 BV / h, and the eluent was collected.

[0050] (3) Diaphragm electrolytic enrichment: The eluent was transferred into a diaphragm electrolytic cell. The cathode was a titanium-plated platinum electrode and the anode was a graphite electrode. The current density was controlled at 90 A / m², the electrolysis temperature was 48 °C, and nitrogen gas was introduced into the cathode chamber (gas flow rate 0.25 L / min). Electrolysis was carried out for 2.2 h to obtain a palladium-rich solution with a palladium concentration of 35 g / L.

[0051] (4) Chemical purification: Add 1.2 mol / L ammonia to the palladium-rich solution, adjust the pH to 8.1, stir for 22 min, and filter; add 2.2 mol / L hydrochloric acid to the filtrate to acidify to pH 1.1, let stand for 1.2 h to precipitate dichlorodiamminepalladium; wash the precipitate three times with a mixture of deionized water and anhydrous ethanol (volume ratio 1:1), then add 11% hydrazine hydrate solution (the amount added is 0.85 times the mass of the precipitate), reduce at 62℃ for 32 min, filter, dry to obtain palladium powder, the purity is 99.993%, and the palladium recovery rate is 99.7%.

[0052] As can be seen from the data in the above embodiments, the technical solution of the present invention is as follows:

[0053] 1. High recovery efficiency: The specific adsorption of palladium ion imprinting resin enables palladium recovery rate ≥99.5% and silver direct recovery rate to remain above 99.2%, which is far superior to traditional processes;

[0054] 2. High product purity: The purity of palladium powder after chemical refining can reach 99.99%, meeting the application requirements of high-end fields such as electronics and catalysts;

[0055] 3. Green and environmentally friendly: No toxic reagents such as cyanide are used throughout the process. The eluent and electrolytic waste liquid can be recycled after simple treatment, without secondary pollution.

[0056] 4. Strong industrial feasibility: The process steps are simple, the equipment investment is low, the resin can be repeatedly recycled and reused, reducing production costs and making it suitable for large-scale industrial production.

Claims

1. A method for preparing a palladium ion-imprinted resin, comprising the following steps: A) Preparation of the prepolymerization system: Add 2-4 mmol / L of dimethylglyoxime to a palladium ion standard solution with a concentration of 0.5-1.0 mmol / L, and stir for 30-40 min; then add 10-15 mmol / L of ethylene glycol dimethacrylate and 0.05-0.1 mmol / L of 2,2-azobisisobutyronitrile, and continue stirring for 15-20 min to obtain the prepolymerization system mixture; B) Precipitation polymerization reaction: After purging the prepolymer system mixture with nitrogen to remove oxygen for 20-30 minutes, the temperature is raised to 60-65℃ and polymerized at a constant temperature for 6-8 hours under nitrogen protection. C) Template ion elution: After the polymerization reaction is completed, filter, wash the precipitate with ethanol, soak in a 5-8% thiourea-hydrochloric acid mixture for 8-10 hours, filter, wash the precipitate with deionized water until the pH of the filtrate is neutral, and obtain the eluted polymer. D) Drying and sieving: The eluted polymer is placed in a vacuum drying oven at 60-70℃ and dried for 12-16 hours. After drying, it is sieved through a standard sieve to collect particles with a diameter of 0.3-0.8 mm, which are palladium ion imprinted resins.

2. The method for preparing palladium ion imprinted resin according to claim 1, characterized in that: In step (A), the palladium ion standard solution is a palladium ion solution with a concentration of 0.5-1.0 mmol / L, using acetonitrile as the solvent.

3. The method for preparing palladium ion imprinted resin according to claim 1, characterized in that: In step (B), the stirring rate is maintained at 120-150 r / min during the polymerization process.

4. The method for preparing palladium ion imprinted resin according to claim 1, characterized in that: In step (C), the mixture is stirred once every 1-2 hours during the soaking process.

5. A method for recovering palladium from a silver electrolyte, comprising the following steps: (1) Pretreatment: After adjusting the pH of the silver electrolyte containing palladium ions to 1-2, sodium bisulfite is added and stirred to dissolve, thus obtaining the pretreated solution; (2) Ion imprinted adsorption: The pretreated solution was passed through a palladium ion imprinted resin adsorption column at a flow rate of 2-4 BV / h. After adsorption saturation, it was eluted with a 6% thiourea-hydrochloric acid mixture to obtain the eluent. (3) Diaphragm electrolytic enrichment: The diaphragm electrolytic cell is divided into a cathode chamber and an anode chamber by a cation exchange membrane. The cathode is a titanium-plated platinum electrode and the anode is a graphite electrode. The eluent is transferred into the anode chamber of the diaphragm electrolytic cell. During the electrolysis process, nitrogen gas is introduced into the cathode chamber. The current density is controlled at 90-110 A / m², the electrolysis temperature is 40-60℃, and the electrolysis is carried out for 2-3 hours. The cathode chamber obtains a palladium-rich solution. (4) Chemical purification: Add ammonia to the palladium-rich solution until the pH value is 8-9, stir for 10-40 min, and filter; add hydrochloric acid to the filtrate to acidify until the pH value is 1-2, let stand for 1-2 h to precipitate; wash the precipitate with a mixture of deionized water and anhydrous ethanol, add hydrazine hydrate solution, reduce at 50-80℃ for 20-60 min, filter and dry to obtain palladium powder.

6. The method for recovering palladium from silver electrolyte according to claim 1, characterized in that: In step (1), after adjusting the temperature of the silver electrolyte containing palladium ions to 30-40℃, the pH value is adjusted to 1-2 with dilute sulfuric acid.

7. The method for recovering palladium from silver electrolyte according to claim 1, characterized in that: In step (1), the amount of sodium bisulfite added is 0.01-0.05 g / L.

8. The method for recovering palladium from silver electrolyte according to claim 1, characterized in that: In step (2), the chloride ion concentration is controlled at 5-7 g / L during the adsorption process.

9. The method for recovering palladium from silver electrolyte according to claim 1, characterized in that: In step (2), the palladium ion imprinted resin in the adsorption column has a particle size of 0.3-0.8 mm.

10. The method for recovering palladium from a silver electrolyte according to claim 1, characterized in that: In step (2), after the resin adsorption column is saturated, a thiourea-hydrochloric acid mixture with a mass concentration of 6% is used for elution at a flow rate of 1-2 BV / h.

11. The method for recovering palladium from a silver electrolyte according to claim 1, characterized in that: In step (3), during the electrolysis process, the nitrogen gas flow rate into the cathode chamber is 0.2-0.4 L / min.

12. The method for recovering palladium from silver electrolyte according to claim 1, characterized in that: In step (4), the amount of hydrazine hydrate added is 0.9 times the mass of the precipitate.

13. The method for recovering palladium from silver electrolyte according to claim 1, characterized in that: In step (4), the volume ratio of water to anhydrous ethanol in the mixture is 1:1.